National Dental Examining Board of Canada (NDEB) Practice Exam 2026 - Free NDEB Practice Questions and Study Guide

When the diameter of a round SS orthodontic wire is doubled, its cross-sectional area is quadrupled, which means that the wire is now four times stiffer. This decrease in flexibility reduces its springiness by 8 times, making option D the correct answer. Option A, 2 times, is incorrect as doubling the diameter does not have a linear effect on the stiffness and springiness of the wire. Option B and C, which suggest a decrease by 4 or 6 times, are also incorrect as they do not accurately reflect the increase in stiffness and decrease in springiness that occurs when the diameter is doubled. Option D is the best and most accurate choice.